The study of pediatric sarcomas is ongoing in two areas: biological studies and therapeutic trials. The biological studies include: (1) in vitro tissue culture evaluation and characterization of cell lines derived from these tumors; (2) in vitro differentiation of cell lines derived from these tumors; (3) cytogenetic characterization of these tumors. The therapeutic studies are attempting: (1) to improve therapy for newly diagnosed patients by intensifying the induction therapy and replacing maintenance with a conslidation therapy including autologous bone marrow transplantation; (2) to develop new therapies for treatment of patients with sarcomas, using Phase II studies of chemotherapeutic agents in relapsed patients. Since the inception of this program, we have demonstrated that Ewing's sarcoma and peripheral neuroepithelioma cell lines have translocation - t (11.22) - and a similar pattern of oncogene expression. We have also demonstrated that with differentiation, the Ewing's sarcoma cell lines develop a nerual phenotype. Since 1983, we have treated over 70 patients with newly diagnosed high risk sarcomas. The complete remission rate on this 83-C-73 protocol is 93% and approximately 50% of the patients remain in remission. These figures represent improvement over previous regimen utilized at this institution. Based on a previous Pediatric Branch Phase II Trial for the treatment of recurrent sarcomas that demonstrated the activity of Ifosfamide, we began a trial in June 1985 utilizing Ifosfamide and Etoposide with Mesna uroprotection. We have now demonsrated that this combination has a high degree of activity in the treatment of recurrent sarcomas in children and young adults. To date, 25 to 49 patients who are presently evaluable have had a complete or partial response. These results suggest that the combination of Ifosfamide and Etoposide will be an important therapeutic combination in the treatment of pediatric malignancy.